Pollution by PCBs poses a threat to whales and dolphins

By Jim Hurley - Nature Trail

When analysed for pollution, tissue samples from a Killer Whale stranded in Co Waterford returned some of the highest concentrations recorded anywhere for that species in an international study of pollution in dolphins.

Dr Simon Berrow, Chief Science Officer of the Irish Whale and Dolphin Group (IWDG) and lecturer on the Applied Marine Biology degree course in the Galway-Mayo Institute of Technology, was one of the co-authors in the pan-European study involving 31 partners.

The pollutants that the study focused on were man-made chemicals called polychlorinated biphenyls (PCBs) a group of persistent organochlorine pesticides. PCBs are well-known to be toxic to birds, fish and mammals. In humans, PCBs have been shown to have a wide-ranging impact on health from links to cancers, suppressing the immune system and causing reproductive failure.

PCBs were first domestically manufactured in 1929 and were used in hundreds of industrial and commercial applications from electrical transformers to paints, plastics, and rubber products. They were banned in America in 1979, in Britain in 1981 and in the rest of the European Union in 1987. Though officially 'gone', their toxic legacy lives on via leakages from landfill and re-suspension during dredging at sea.

PCB residues persist in tissues and accumulate as one goes up the food chain so, since dolphins are top predators of their food chains, they are particularly vulnerable to poisoning and are therefore important animals to monitor. Bottlenose Dolphins and Killer Whales in Ireland were among the animals studied in the recent investigation.

While, on the one hand, the Killer Whale from Co Waterford had exceptionally high levels of PCBs, on the other hand, Bottlenose Dolphins in the Shannon Estuary had the lowest levels of these toxic chemicals in Europe. On the face of it, that sounds like good news but the experts caution that these low levels are levels that are still well above the toxicity threshold of serious impacts.

Even though these nasty chemicals have been banned since the 1980s they have not gone away. The levels of PCBs found in dolphin blubber during the recent study were not just high but were far higher than what the scientists expected they would be.

The recently published report of the pollution study is available online at http://www.nature.com/articles/srep18573. For further information about Killer Whales and dolphins and/or to support their conservation work, see the website of the Irish Whale and Dolphin Group at www.iwdg.ie